This invention relates to a control circuit for controlling selected functions of a signal receiver, such as a television receiver, and more particularly, to such a control circuit which is responsive either to remotely generated control signals or to the operation of manual controls which are provided on the signal receiver.
In operating a signal receiver, such as a television receiver, it often is desirable to control the functions of that receiver either by the direct manual operation of suitable control switches which are provided on the receiver, or from a remote location. For example, and with respect to a television receiver, the power on/off function, the audio volume function and the channel selecting function can be controlled by these alternate means. Of course, in a conventional television receiver, a power on/off switch, an audio gain-controlled amplifier and an electronic tuner generally are provided for these functions. The television viewer merely operates the appropriate switches and control knobs in order to selectively control the various functions, or operations associated therewith. In addition, it is conventional to provide a control signal receiver which is adapted to receive remotely generated control signals for controlling many of the same functions which are controlled by the aforementioned switches and knobs.
Typically, to achieve remote control of a television receiver, the viewer is provided with a portable sonic or ultrasonic transmitter, and the television receiver is provided with a compatible sonic or ultrasonic receiver and decoder. The sonic or ultrasonic signal which is transmitted by the portable transmitter generally has a particular frequency component which is associated with the respective function to be controlled. For example, the power on/off function may be associated with one frequency, an increase in the audio volume may be associated with another frequency, a decrease in the audio volume may be associated with yet another frequency, and the selection of various channels may be associated with further respective frequencies. In some television receivers having this remote control capability, the sonic or ultrasonic receiver and decoder are separate and distinct from the manual controls which are provided directly on the receiver. That is, when the manual controls are operated, the remote control signal decoder is not used. This results in additional components for the television receiver, with a concomitant increase in cost.
With the advent of electronic tuners and integrated circuits, it is advantageous to provide a single control circuit which is responsive either to remotely generated control signals or to the operation of manual controls for selecting and controlling various functions of the television receiver. For example, the control circuit, which preferably is constructed as an integrated circuit, may include a decoder for decoding the received sonic or ultrasonic control signals and a channel selecting circuit which is responsive either to the decoded channel select signals, which are transmitted from the remote transmitter, or to the operation of channel selecting switches. The channel select circuit then is used to generate a tuning control voltage for selecting the desired channel to which the television receiver is to be tuned.
One disadvantage of the control circuit of the aforedescribed type is that, to provide a single control circuit, constructed as an integrated circuit, which is responsive either to a remotely generated control signal or to the operation of manual switches requires a large number of input terminals for the integrated circuit. That is, each manual switch generally must be connected to a respective integrated circuit input terminal. In general, the cost of manufacturing an integrated circuit is dependent, to some degree, upon the total number of input and output terminals which must be provided. Hence, the integrated circuit which is used as this control circuit is relatively expensive. Although the number of input terminals can be reduced if the integrated circuit is provided with an input stage of matrix configuration, such an integrated circuit still is relatively expensive to manufacture. A further reduction in the number of input terminals can be obtained by connecting the manual controls to the control circuit via an encoder. However, the reduction in cost attributed to the decrease in number of input terminals is accompanied by an increase in cost due to the requisite encoder.
Another disadvantage of the aforedescribed type of control circuit, even if provided with an input stage of matrix configuration or a signal encoder, is that the manual controls which are used to select the power on/off function and the audio volume adjustment function generally are not connected to the input circuit. As a consequence thereof, separate connections must be made between manual controls and the power supply and the audio amplifier, respectively, thereby increasing the cost of assembly. Moreover, the control circuit is not utilized efficiently.